Resonant-cavity magnetron having co-axial output line



March 28, 1961 w. SCHMIDT ET AL 2,977,503

RESONANT-CAVITY MAGNETRON HAVING CO-AXIAL OUTPUT LINE Filed Sept. 3. 1958 IN NTOR WOL FGA SCHMIDT GERHARD W. SOHUHMANN AGENT United States Patent RESONANT-CAVITY MAGNETRON HAVING CO-AXIAL OUTPUT LINE Wolfgang Schmidt, Hamburg-Othmarschen, and Gerhard Werner Schuhmaun, Hamburg, Germany, assignors to North American Philips Company, Inc., New York, N.Y., a corporation of Delaware Filed Sept. 3, 1958, Ser. No. 758,716

Claims priority, application Germany Sept. 5, 1957 2 Claims. (Cl. SIS-39.53)

This invention relates toresonant-cavity magnetrons having co-axial outut lines which terminate inside the magnetron in loop-like members.

Magnetrons having output lines of the above-mentioned kind are universally known. However, a problem is to make the surface area of the looplike member sufficiently large. When the surface area of'the loop is small, excessive losses may occur and also an unduly low coupling with the load results. If the loop is chosen of heavy material and with a larger surface area, an unduly strong capacitive load on the resonant cavity of the magnetron occurs.

A structure is also already known in which an aerial loop in a wave guide outside the magnetron merges at its end into two loops which are connected to sequential anode segments, thus being located either in one or in two sequential resonant cavities and being led separately to the exterior. In the second case, a more satisfactory separation of modes is obtained. However, both structures have the disadvantage that the output coupling has a high impedance and is not suitable for connection to a co-axial line.

An object of the invention is to provide a structure which affords advantages with respect to the known design. 7 I

According to the invention, in a resonant-cavity magnetron having a co-axial output line which inside the magnetron merges into a, loop-like member, the inner conductor of the co-axial output line terminates in a recess of an anode segment to merge into two loops in sequential resonant cavities, which loops terminate on the non-sequential anode segments'bounding said resonant cavities.

The structure according to the invention permits of obtaining a large surface area of the loop without unduly high capacitances being involved, whilst also the ohmic resistance is low due to the parallel connection and the output coupling has a low impedance due to the parallel combination of the loops; 7 The coupling has a favourable ratio of transformation and a favourable degree of coupling.

A simple embodiment of the structure according to the invention is that in which the inner conductor of the co-axial line in the recess of the relevant anode segment merges into a single conductor extending at right angles thereto. In this manner a robust structure is obtained. In order that the invention may be readily carried into efiect, two embodiments will now be described in detail, by way of example, with reference to the accompanying drawing, in which Figs. 1 and 2 each show diagrammatically part of the anode system of a magnetron with its output line according thereto.

In Fig. l, the outer side of the anode is indicated by 1 and the anode segments are indicated by 2. The co-axial line having an inner conductor 3 and an outer conductor 4 is fixed in an opening at the foot of one anode 7 segment. In the recess of the central one of the three anode segments shown, the inner conductor merges into arcuate loops 5 and 6, which terminate at the foot of anode segments oscillating with the same phase. A given instantaneous condition of oscillation is represented with loads on the extremities of the anode segments and by arrows indicating the direction of the magnetic field.

Fig. 2 difiers from Fig. 1 insofar that inner conductor 3 extends a little further towards the interior to merge thereinto a straight conductor 7, 8 which is attached to two anode segments at 9 and 10.

What is claimed is:

1. In a magnetron comprising an anode block defining a main cavity and a plurality of cavity resonators opening into the main cavity, said anode block having anode segments separating the cavity resonators from each other, a coaxial output line coupled to said magnetron comprising an inner conductor terminating in a recess of an anode segment remote from the main cavity, a pair of loop-like conductors eachof which is disposed in the rear portion of a resonant cavity bounded on one side by said anode segment, each of said loop-likeconductors being connected at one endto said inner conductor and at the other ,end terminates on abounding. I

surface of another anode segment bounding each of said resonant cavities. g I H l 2. A resonant-cavity magnetron as claimed in claim 1,

in which the two loops together constitute a straight continuous conductor.

References Cited in the file of this patent UNITED STATES. PATENTS 

